Route guidance devices are heretofore known which are configured to guide a route to a designated destination while being reflected with an isolated intersection at which there is the risk for a vehicle to be isolated without smoothly passing through the intersection. For example, JP2012-247315A discloses a route guidance device in which a risk value matrix is prepared for each factor feature, such as a railroad crossing and a lane decreased portion of a road, which exists in the leaving direction from an intersection. The risk value matrix gives a risk value score that indicates the possibility that the intersection can be an isolated intersection. For a search result of the route from a starting point to a destination, the route guidance device refers to the risk value matrix for each intersection on that route to obtain the risk value score and extracts, as the isolated intersection, an intersection at which the risk value score exceeds a predetermined threshold. Then, the route guidance device searches and guides a route that allows avoidance of the isolated intersection.
Drive assist vehicles or autonomous drive vehicles perform an action decision of the vehicle and travel while recognizing traffic signals and the like. In such vehicles performing the action decision, information necessary for the action decision has to be collected for an appropriate drive.
In the above technique of JP2012-247315A, however, the index of the degree of risk is based on whether there is the risk for a vehicle to be isolated at an intersection. Thus, even when the degree of risk is low at an intersection, the vehicle deciding the action cannot recognize traffic signals and the like due to factors, such as the road shape of the intersection and the positions of the traffic signals, and cannot appropriately travel.